1. Field of the Description
The present invention relates, in general, to devices and methods for providing a three-dimensional (3D) display in a glasses-free manner, and, more particularly, to a display system adapted for using a horizontally-oriented display (e.g., “a 3D tabletop display”) to display high quality 3D images (left and right eye images) to one or more viewers' eyes that can be viewed without the need for the viewer to use special glasses, headgear, or filters (e.g., glasses-free 3D or autostereoscopic) as the viewers are free to move all around the display such that it functions as a 360-degree autostereoscopic tabletop display.
2. Relevant Background
Displays that provide the illusion of three dimensions have experienced a rebirth in the past few years. For example, a number of 3D televisions are now available for use in homes and home theaters. These 3D televisions generally operate by displaying a stream of left and right eye images in an alternating or time-multiplexed manner (e.g., left-right-left-right). Switching occurs so quickly that the viewer does not sense a flicker or change in the display. The viewer wears special headgear or glasses that operate in a synchronized manner with the display to only allow the light associated with the left eye image to reach the viewer's left eye and with the right eye image to reach the viewer's right eye.
While most commercial displays rely on the use of special glasses, it is generally agreed by those in the 3D entertainment industry that displays able to provide a 3D viewing experience without glasses or headgear offer significant advantages. Autostereoscopy is any method of displaying stereoscopic images (i.e., adding binocular perception of 3D depth) without the use of special glasses or headgear on the part of the viewer. Many autostereoscopic or glasses-free 3D displays have been developed using a variety of technologies including lenticular lenses on the display screen combined with interlaced content, screens configured as parallax barriers, volumetric displays, and holographic and light field displays. However, each display technology has to date been proven to have limitations that have limited their widespread adoption.
For example, 3D televisions have been configured as lenticular autostereoscopic displays. The 3D lenticular television is mounted vertically on a wall or on a support base, and a viewer has multiple view images directed toward their eyes through a plurality of lenticules (or elongated lenses) that extend vertically upward or in a slanted manner upward on the outer surface of the display monitor. The 3D lenticular television may provide 1920 by 1200 pixels that are used to display an 8-view autostereoscopic image through the lenticules (or lens array or lenticular sheet). To this end, the image content (or digital image file) is interdigitated or interlaced as a number of slices (e.g., 8 slices in this example) of images that include multiple view images to provide the 3D effect, and the set of interlaced slices are displayed and repeated under each lenticule. These 3D televisions have a number of drawbacks in practice. The viewer typically has to remain in a particular location relative to the front surface (lenticular sheet) of the display/monitor such as directly in front of the display/monitor and with their head (and left and right eyes) at a predefined height (e.g., a height matching the center of the display/monitor). The lenticular 3D television only provides views horizontally so if the viewer is at too great of a height (or too low of a height) the 3D image is viewed from an incorrect perspective, resulting in a distorted image that appears in an undesirable or unrealistic manner.
More recently, there has been a demand in the 3D display industry for an autostereoscopic tabletop display (e.g., a horizontal display) adapted for use by multiple viewers that are free to move fully around the tabletop display to provide a 360-degree display device. These types of devices allow the users or viewers to observe and interact with displayed 3D content that shares the same 3D space as real world objects such as 3D objects (e.g., game pieces, model objects for 3D design, and the like) placed on the table or near its upper, exposed surface. Such autostereoscopic tabletop displays are desirable because they allow interactive experiences such as for visitors of an entertainment facility (e.g., an amusement park), facilitate collaborative design among two or more designers or engineers as they can quickly visualize 3D objects and move them in a 3D space relative to each other (e.g., support computer-aided design), and would be useful in many educational settings.
Many commonly used concepts for vertical autostereoscopic displays cannot be readily applied to a 360-degree autostereoscopic tabletop display. For example, lenticular lens and static parallax barrier-based, multi-view displays can only provide parallax in one direction, which would not support a viewer moving around the outside periphery of a tabletop display (e.g., would not support a 360-degree display). Integral 3D displays using lenslet arrays can offer parallax in two directions, but, like lenticular lens and static parallax barrier-based displays, these displays suffer from small viewing angles and periodic view repetition.
Another well-explored approach to 360-degree autostereoscopic displays involves using high-speed projectors that generate a large amount of views in combination with rotating anisotropic projection screens to redirect the views in the appropriate direction. In some of the designs, the rotating projection screen intersects with the displayed volume while others use a flat screen to create a tabletop display. Still others have used a known optical illusion using two facing parabolic mirrors to re-image the rotating screen above the tabletop display's surface. While useful in some applications or settings, a common drawback of all of these systems is the low bit-depth of all displayed images due to the nature of the high-speed projectors and the fast-spinning projection screens.
Light field displays with a large number of views at full resolution and bit-depth can be achieved using an array of projectors. Using a special conical-shaped diffuser, this approach has been adapted to a 360-degree tabletop display. However, an obvious drawback of these designs is the very high cost associated with the required large number (e.g., hundreds) of projectors. Furthermore, the calibration of the projectors can be especially challenging.
Hence, there remains a need for a new design for an autostereoscopic tabletop display. Preferably, this new design will allow a viewer or user of the display to move freely around the entire periphery of the display to provide a 360-degree display. Also, it is preferable that the new design provide a less complex device with fewer components (e.g., without the need for hundreds of projectors), fewer moving parts (e.g., without spinning projection screens), and fewer operational challenges (e.g., less calibration challenges).